I think both Thor and Cap will do fine. In both you have big players from Avengers, people will want to check them out.Guardians of the Galaxy, on the other hand, is a huge question mark for me. Don't know how's that gonna be received.

Brand with good marketing from Disney will ensure the film will have awareness. If the movie is good and generates positive WOM then it will do fine, and given the potential of the subject matter I'd give it a good shot at hitting $600m if not more.